Abstract
Gut microbiota play an important role in metabolism of intake saponins, and parallelly, the polysaccharides deriving from herbal products possess effects on gut microbiota. Ophiopogonis Radix is a common Chinese herb that is popularly used as functional food in China. Polysaccharide and steroidal saponin, e.g., ophiopogonin, mainly ophiopogonin D (Oph-D) and ophiopogonin D’ (Oph-D’), are the major constituents in this herb. In order to reveal the role of gut microbiota in metabolizing ophiopogonin, an in vitro metabolism of Oph-D and Oph-D’ by human gut microbiota, in combination with or without Ophiopogon polysaccharide, was conducted. A sensitive and reliable UPLC-MS/MS method was developed to simultaneously quantify Oph-D, Oph-D’ and their final metabolites, i.e., ruscogenin and diosgenin in the broth of microbiota. An elimination of Oph-D and Oph-D’ was revealed in a time-dependent manner, as well as the recognition of a parallel increase of ruscogenin and diosgenin. Ophiopogon polysaccharide was shown to stimulate the gut microbiota-induced metabolism of ophiopogonins. This promoting effect was further verified by increased activities of β-D-glucosidase, β-D-xylosidase, α-L-rhamnosidase and β-D-fucosidase in the broth. This study can be extended to investigate the metabolism of steroidal saponins by gut microbiota when combined with other herbal products, especially those herbs enriched with polysaccharides.
Highlights
Ophiopogonis Radix, the tuberous roots of Ophiopogon japonicus (Thunb.) Ker-Gawl. (Liliaceae), known as Maidong in Chinese, is a common herb being used either as a health food or a therapeutic agent for prevention and treatment of diseases [1]
The multiple reaction monitoring (MRM) in positive ion mode was identified for each ophiopogonin (i.e., ophiopogonin D’ (Oph-D), Oph-D’, ruscogenin and diosgenin), considering sensitivity and reproducibility of dominant ions in full-scan mass spectra, as reported previously [20,21]
Formation of ruscogenin/diosgenin, and which indicated that Ophiopogon polysaccharide could significantly promote the metabolism of ophiopogonins
Summary
Ophiopogonis Radix, the tuberous roots of Ophiopogon japonicus (Thunb.) Ker-Gawl. (Liliaceae), known as Maidong in Chinese, is a common herb being used either as a health food or a therapeutic agent for prevention and treatment of diseases [1]. Ophiopogonis Radix, the tuberous roots of Ophiopogon japonicus (Thunb.) Ker-Gawl. The main components of Ophiopogonis Radix include steroidal saponins, homo-isoflavonoids, and polysaccharides. Pharmacologic studies have revealed the activities of Ophiopogonis Radix and its ingredients, including cardiovascular protection, immunomodulation, anti-diabetic, anti-inflammation, anti-cancer, and anti-oxidation activities [1,2,3]. Steroidal saponins are the major active constituents in Ophiopogonis Radix, having two major types: the ruscogenin-type (Rus-type) and the diosgenin-type (Dio-type). Oral pharmacokinetic study revealed the low oral bioavailability of Rus-type and Dio-type steroidal saponins [4,5]. Ruscogenin and diosgenin were reported to be the metabolites of Rus-type and Dio-type steroidal saponins, which were being absorbed into the blood [6,7].
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